From personal experience, I've found that the OTC product Imodium AD is very effective in stopping diarrhea. Follow the directions, experience the relief.
Immodium is a good over the counter medicine, just taking one or two pills should stop it. But be aware it will stop it for a while so you may not have a bowel movement for a while after you take it.
Anti-emetic medicines, such as : Immodium AD, Kaopeptac and Lomotil, are effective in stopping diarrhea. However, it is best to let it run its' course!
Usually diarrhea stops on its own with in 2 days. Some times though you can't wait because of work or errands. Imodium is over the counter and works great, usually with one dose. Be sure to also stay hydrated through out this.